Method of growing iridium substituted single crystal using bismuth oxide flux



Jack A.. liohn, New Shrewsbury, Robert G. Savage, Era,

Qpltriyi'flbd Fatenteri Dec. 22,

of the device in which it is incorporated; single crystals intrinsically have narrower line widths; (2) several useful properties are observed only in single crystals; single crystals are important as standards by which to evaluate the performance of polycrystalline materials of the same l leptuue Qi'ty, and Arthur Timber, Ether-on. Ni, asa composition.

fiigml'a the Mfiiiefi glides Amiifiw l It has been found that the aforementioned objectives the i .2? i 1 1 can be attained by a method involving mixing (a) ferric N0 z, glfl W-figiffg? 2969251. oxide, (5) barium oxide or barium carbonate, (0) an (Granted. uncles i l ill ssiiisfc risiiisn, sec. 26s Oxide the group l fl f h magnesium, manganese, iron, zinc, or copper, (d) iridium The invention described herein may be manufactured or iridium oxide and (e) bismuth oxide either dry or with and used by or for the Government for governmental a dispersing agent such as water or ethyl acetate, drying purposes without the payment of any royalty thereon. the mixture, heating the mixture in a platinum or iridium This invention relates to a method of growing single crucible between 1200 and 1300 C., slowly cooling the crystals of the general formula BaFe (lr l/le; )O; melt l to 4 C. per hour to 950 C., and removing the where Me is a divalent metal from the group cobalt, crystals from the crucible by leaching with hot dilute nickel, magnesium, manganese, iron. zinc, or copper and nitric acid (l()% by volume). Tue single crystals where x is a number from 0 to 0.6. obtained exhibit black very lustrous, well developed An object of this invention is to grow single crystals 20 crystallographic faces. individual crystals measure up to of the above general formula that are mechanically sound, /1 inch on an edge. The crystals possess both axial and}; have well developed crystalline faces and are relatively planar magnetic anisotropy. The elfective axial anisotfree of microscopic pits and foreign inclusions. Anropy eld of the crystals can be varied from 17,000 other object is to grow single crystals of the above general towards 0 ocrsteds by controlling the iridium concentraformula for use in microwave and millimeter device aption. Crystals can also be grown having an effective plications as in isolators, rotators, filters. power limiters, planar anisotropy field from near 0 oersteds to at least and harmonic generators. A further object is to grow 22,000 oersteds. These large anisotropy field changes single crystals of the above general formula that can be are accompanied by a relatively small decrease in satura recovered byasimple chemical treatment. A still further tion magnetization and Curie temperature. X-ray difobject is to grow such single crystals at a melting tem- 3 fraction powder and single crystal patterns show that perature sufficiently low to eliminate the problem of the these crystals have the ferroxdure (BaFe O structure reduction of Fe, thus improving the electronic properand that the cell volume increases with increasing x. ties of the product. A further object is to grow the Some of the single crystals grown according to the single crystals at a temperature that greatly reduces the method of the invention with the Batch Starting Composiloss of volatile components. Another object is to grow 5 tion and resulting magnetic properties are listed in the single crystals possessing both axial and planar magnetic following table.

TABLE Preparation and Properties of Single Crystals in the System BaFe lr lvle O Magnetic Properltcs Actual Chemical Coin Batch Starting Comlvlngnctization position position Units, cxnfi/g. Magnetic Curie Moment Temp. Anisotropy Field in Fcrrlmag. Line in us C. ocrsteds Width in oersteds Room Bl. Temp. Liq. Nib.

' l 1. Dal-c 1 01 2 moles BoCOi, 2 moles 72 103 20 .50 Axial Anisotropy 53 55 KMC.

Znt), ll moles F020;. 1 Ilu==l7,0t)t). mole lit- 0 in a platinum crucible. 2. Bn'te 11.05 IrunZn 0 Same as 1. plus 4 wt. pcr- 64 102 20.7 3L Axlnl Anisotropy cont II'Og in a platinum 11,500. crucible. 3. BaF0m su Ir Zu O Same as 1. pcrtormcd in a 47 73 18.9 217 llnuar Anisotropy 1.175 @15 KMC. Iridium crucible. 23,1100. 4. Bel o Irma Znn, Om." Sumo as 1. plus 8.3 wt. per- 59 so 2&7 Planar Anisotropy. 105 17 KMC.

cent lll lllllll metal. I

it can be seen from the table that the single crystals prepared by the method of the invention represent an effective anisotropy field range of from 17,000 oersteds axial in the case of ferroxdure (BaFe O to 22,000 oersteds planar in the case of BaEe lr Zn O Thus the method lends itself to the growing of single crystals in which one can control the anisotropy properties.

In the method of the invention, bismuth oxide (M 0 serves as the fluxing agent. The bismuth oxide acts as a solvent for the iridium. As oxidation of iridium metal at the temperatures and times employed is appreciable, the melt may contain iridium oxide or iridium metal.

It is preferred to use a platinum crucible in carrying out the method as the amount of iridium introduced can then be critically controlled. An excess of up to 50 mole percent iridium is introduced into the initial melt in view of the volatility of the iridium and the competing side reactions occurring during the formation of the single crystals. The amount of the iridium that will go into the single crystal is alsov determined by such factors as the maximum temperature to which the melt is raised and the cooling rate ofthe melt. The amount of iridium that can be introduced into the melt is controlled by its solubility in bismuth oxide at a particular temperature.

In the method, the initial mixture may contain from 45.5 to 50.0 mole percent Bi O 9.1 to 12.5 mole percent BaO, 27.3 to 37.5 mole percent F6203, 9.1 to 12.5 mole percent divalent metal from the group cobalt, nickel, magnesium, manganese, iron, zinc, or copper and 0 to 9.1 mole percent iridium.

The foregoing description is to be considered only as illustrative of the invention and not in limitation thereof.

What is claimed is:

1. The method of growing singlecrystals of the general formula BaEe (Ir Me )O Where Me is a divalent metal selected from the group consisting of cobalt, nickel, magnesium, manganese, iron, zinc, and copper and where x is a number from 0.16 to 0.6 said method comprising (1) mixing (a) ferric oxide, ([7) barium oxide, (0) an 1 oxide of a divalent metal taken from the group consisting of cobalt, nickel, magnesium, manganese, iron, zinc, and copper, (d) iridium and (e) bismuth oxide, (2) heating the mixture in a metallic crucible selected from the group consisting of platinum and iridium between 1200 and 1300 C., (3) slowly cooling the melt 1 to 4 C. per hour to 950 C., and (4) removingthe crystals from the crucible by leaching with 1020 percent by volume nitric acid.

2. The method according to claim 1 where single crystals of the formula BaFe 1r Zn O are grown.

3. The method according to claim 1 where singlecrystals of the formula BaFe lr Zn O are grown. 4. The method according to claim 1 where single crystals of the formula BaFe i'r Zn o are grown.

References Cited by the Examiner UNITED STATES PATENTS 8/58 Remeika 23305 2/63 Remeika 23-305 OTHER REFERENCES MAURICE A. BRINDISI, Primary Examiner.

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1. THE METHOD OF GROWING SINGLE CRYSTALS OF THE GENERAL FORMULA BAFE12-2X(IRXMEX)O19 WHERE ME IS A DIVALENT METAL SELECTED FROM THE GROUP CONSISTING OF COBALT, NICKEL, MAGNESIUM, MANGANESE, IRON, ZINC, AND COPPER AND WHERE X IS A NUMBER FROM 0.16 TO 0.6 SAID METHOD COMPRISING (1) MIXING (A) FERRIC OXIDE, (B) BARIUM OXIDE, (C) AN OXIDE OF A DIVALENT METAL TAKEN FROM THE GROUP CONSISTING OF COBALT, NICKEL, MAGNESIUM, MANGANESE, IRON, ZINC, AND COPPER, (D) IRIDUM AND (E) BISMUTH OXIDE, (2) HEATING THE MIXTURE IN A METALLIC CRUIBLE SELECTED FROM THE GROUP CONSISTING OF PLATINUM AND IRIDIUM BETWEEN 1200 AND 1300*C., (3) SLOWLY COOLING THE MELT 1 TO 4*C. PER HOUR TO 950*C., AND (4) REMOVING THE CRYSTALS FROM THE CRUCIBLE BY LEACHING WITH 10-20 PERCENT BY VOLUME NITRIC ACID. 